WorkingHours displays that warning whenever the background task didn't run in the past 6 hours - it doesn't check if it's already exempt or not. It's possible that the Android OS blocks the execution of the background task even though you allowed background usage (e.g. when you use power saving mode). It's also possible that there are other (perhaps manufacturer-specific) settings that might block background execution. Or you turned on your phone and launched WorkingHours right away, in which case the background task also wasn't able to run in the last 6 hours. You see, lots of possibilities, and WorkingHours cannot check them all individually. So if you are bothered by the prompt, you can simply click "Don't show this again"
